Electric discharge machining of a probe array

ABSTRACT

A method of forming a probe away includes forming a layer of tip material over a block of probe material. A first electric discharge machine (EDM) electrode is positioned over the layer of tip material, the EDM electrode having a plurality of openings corresponding to a plurality of probes to be formed. Excess material from the layer of tip material and the block of probe material is removed to form the plurality of probes. A substrate having a plurality of through holes corresponding to the plurality of probes is positioned so that the probes penetrate the plurality of through holes. The substrate is bonded to the plurality of probes. Excess probe material is removed so as to planarize the substrate.

This application is a continuation of U.S. application Ser. No.10/302,969, filed Nov. 25,2002, now U.S. Pat. No. 7,122,760.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is related to a method of making an array ofprobes for use in probing electronic devices, such as a probe card forprobing the dies on a semiconductor wafer.

2. Related Art

Semiconductor dies must be tested during the manufacturing process toinsure the reliability and performance characteristics of integratedcircuits on the dies. Accordingly, different testing procedures havebeen developed by semiconductor manufacturers for testing semiconductordies. Standard tests for gross functionality are typically performed byprobe testing the dies at the wafer level. Probe testing at the waferlevel can also be used to rate the speed grades of the dies.

Testing a large number of integrated circuit chips in parallel at thewafer level provides significant advantage since test time and cost aresubstantially reduced. At present, large scale testers includingmainframe computers are needed to test even one chip at a time, and thecomplexity of these machines is increased when the capability of testingarrays of chips in parallel is added. Nevertheless, because of the timesavings parallel testing provides, high pin-count testers capable ofprobing and collecting data from many chips simultaneously have beenintroduced, and the number of chips that can be tested simultaneouslyhas been gradually increasing.

Substantial lower cost would result from an improved wafer test andburn-in scheme that permits parallel test and burn-in of the chips on awafer before dicing.

As wafer testing requirements become more sophisticated, the need forhigh density probes, and efficient and relatively inexpensive methods ofmanufacturing them continues to be a challenge. Accordingly, a needexists for an inexpensive and efficient method of manufacturing highdensity probe array.

SUMMARY OF THE INVENTION

The present invention is directed to a probe array for testing ofsemiconductor wafers and a method of its manufacture that substantiallyobviates one or more of the problems and disadvantages of the relatedart.

There is provided a method of manufacturing a probe array includingforming a first substrate having a plurality of through holes. A secondsubstrate is formed having a plurality of probe tips embedded therein. Aplurality of wires are bonded to corresponding probe tips of the secondsubstrate. The through holes of the first substrate are mated with theplurality of wires. The second substrate is removed. The first substrateis planarized, and connections are formed on the first substrate to theplurality of wires for connecting to external signal sources.

In another aspect there is provided a method of forming a probe arrayincluding forming a layer of tip material over a block of probematerial. A first electric discharge machine (EDM) electrode ispositioned over the layer of tip material, the EDM electrode having aplurality of openings corresponding to a plurality of probes to beformed. Excess material from the layer of tip material and the block ofprobe material is removed to form the plurality of probes. A substratehaving a plurality of through holes corresponding to the plurality ofprobes is positioned so that the probes penetrate the plurality ofthrough holes. The substrate is bonded to the plurality of probes.Excess probe material is removed so as to planarize the substrate.Advantages of the method of making the probe array according to thepresent invention include the use of two stages of steps with twodifferent substrates. Therefore, the processing steps of the two stagescan be carried out in parallel and independent of one another. Anyerrors or defects that may be present require only a repetition of oneset of steps. Also, the resultant probe array has through holes thatprovide support along at least a segment of the probe. The support isespecially advantageous in a probe array with lateral contact movementor wiping.

In another aspect there is provide a probe array including a substrate,and a plurality of probes for contacting test terminals on a testdevice. Each probe has a stem and a tip. Each probe penetrates thesubstrate for support. The substrate has a plurality of through holessuch that the stems of the probes penetrate the through holes and arebonded to the substrate.

Additional features and advantages of the invention will be set forth inthe description that follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theadvantages of the invention will be realized and attained by thestructure and particularly pointed out in the written description andclaims hereof as well as the appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to illustrate exemplaryembodiments of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention. In the drawings:

FIGS. 1-4 illustrate the steps in one method of manufacturing probes fora vertical probe array.

FIGS. 5-6 illustrate the steps of joining the probes illustrated inFIGS. 1-4 with a substrate to form a probe array.

FIGS. 7-8 illustrate the Steps of shaping tips of the probes of theprobe array of FIG. 6.

FIG. 9 illustrates in flow chart form the steps involved inmanufacturing the probe array corresponding to FIGS. 1-8.

FIG. 10 illustrates an alternative EDM electrode that may be used tomanufacture probes of a probe array.

FIG. 11 illustrates a cross-section of the EDM electrode of FIG. 10.

FIGS. 12-16 illustrate an alternative process of making the probes.

FIG. 17 shows loose probes formed according to the process shown inFIGS. 12-16.

FIG. 18 illustrates a base substrate for mounting the probes.

FIG. 19 illustrates a cross-section of the base substrate of FIG. 18.

FIGS. 20-21 illustrate assembly of the probes into an array.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Reference will now be made in detail to the embodiments of the presentinvention, examples of which are illustrated in the accompanyingdrawings.

FIGS. 1-8 illustrate a first method of forming an array of probes, andFIG. 9 shows the steps 901-908 for making the probes as shown in FIGS.1-8 in flow chart form.

As shown in FIG. 1, a block of tip material 101 is attached to a blockof probe material 102 (step 901). The tip material 101 and the probematerial 102 should be conductive, but otherwise may be formed of anynumber of known materials. Examples of suitable tip materials and probematerials include palladium, copper, gold, rhodium, nickel, cobalt,silver, platinum, conductive nitrides, conductive carbides, tungsten,titanium, molybdenum, rhenium, indium, osmium, refractory metals, andalloys or composite compositions including one or more of any of theforegoing. The tip material 101, for example, may be electroplated ontothe probe material 102. The tip material 101 may also be welded,soldered, brazed, etc. to the probe material 102. Of course, the probematerial 102 and/or the tip material 101 may be further treated. Forexample, one or both of the materials may be heat treated or annealed;ions may be implanted into either or both materials; etc. Moreover, suchfurther treatment may be performed at any time during the process,including before the EDM electrodes shape the material and after thematerials are fully shaped by the EDM electrodes. In addition, at anytime during shaping by an EDM electrode, the shaping process may bestopped, and a material treated.

An electric discharge machine (“EDM”) is then used to shape the tipmaterial 101 and probe material 102 into basic probe shapes (steps902-903). A first EDM electrode 201 shaped in the form of the desiredprobe away is applied to the block of tip material 101 and probematerial 102 as shown in FIGS. 2 and 3. After excess material isremoved, the resulting structure is shown in FIG. 4. Probes 401 are thensecured in the through holes 502 of a substrate 501 (which may be madeof, for example, ceramic, silicon, printed circuit board material,etc.), as shown in FIG. 5, using solder 503 or some other suitablejoining material (steps 904-905). Press-fit and thermal-fit techniquesmay also be used. The bottom portion 504 (relative to the orientationshown in FIG. 5) of the probe material 102 is then removed, as shownFIG. 6 (step 906). In one example, excess probe material 102 of bottomportion 504 is removed so as to planarize the substrate. Etching,grinding, polishing, lapping, or other suitable methods may be used toremove the bottom portion 504. Alternatively, portions of the probes 410may be left extending through the bottom (as oriented in FIG. 5) ofsubstrate 501. For example, only the bottom portion 504 may be removed(e.g., using an EDM electrode, etching, etc.). The portions of probes410 that extend through the bottom of substrate 501 may be secured(e.g., by soldering) to another substrate.

As shown in FIG. 7, a second EDM electrode 701 is used to shape the tipmaterial 101 on the ends of the probes 401 by removing excess material(step 907), to result in the structure of FIG. 8. Electrical connections(not shown) are then formed on the first substrate 501 to the probes 401for use in connecting to external test signal sources (step 908). Thestructure shown in FIG. 8 may be used to make a probe card assembly orother apparatus for probing electronic devices. Of course, the tipmaterial 101 may be shaped as in FIGS. 7 and 8 before securing theprobes 401 to the substrate 501.

The EDM electrodes 201 may be formed of any conductive material that canbe etched, machined, or otherwise processed to form the desiredpatterns. For example, the first EDM electrode 201 may he formed ofgraphite, which can be patterned using laser ablation (e.g., using anexcimer laser). As another example, the second EDM electrode 701 may beformed of silicon, which may be highly doped and which can be patternedby etching pits into the surface of the silicon. Optionally, a surfaceof the EDM electrode may be metallized by sputtering, plating, chemicalvapor deposition, and other techniques, or otherwise treated.

Thus, there is provided a method of forming a probe away includingforming a layer of tip material 101 over a block of probe material 102.A first electric discharge machine (EDM) electrode 201 is positionedover the layer of tip material 101, the EDM electrode 201 having aplurality of openings corresponding to a plurality of probes 401 to beformed. Excess material from the layer of tip material 101 and the blockof probe material 102 is removed to form the plurality of probes 401. Asubstrate 501 having a plurality of through holes 502 corresponding tothe plurality of probes 401 is positioned so that the probes 401penetrate the plurality of through holes 502. The substrate 501 isbonded to the plurality of probes 401. Excess probe material is removedso as to planarize the substrate 501. The tip material may be furthertreated before or after forming the probes. For example, the tipmaterial may be treated using ion implantation techniques, plating, etc.

FIGS. 10 and 11 illustrate another exemplary EDM electrode 1002 that maybe used to manufacture probes for a probe array. FIG. 10 shows a bottomview of the electrode 1002, and FIG. 11 shows a cross-sectional sideview of the electrode 1002. As shown, there is a plurality of cavities1004 in the bottom of the electrode 1002. As will be seen, the cavities1004 are in the shape of probes to be made.

As shown in FIGS. 12-14 (in which the electrode 1002 is shown incross-section), the electrode 1002 is brought into contact with probematerial 1206, which may be similar to probe material 102 discussedabove. As shown in FIG. 12, the probe material 1206 may optionally beadhered to a sacrificial material 1208. As shown in FIG. 13, theelectrode 1002 shapes the probe material 1206. As shown in FIG. 14, theelectrode 1002 may also partially shape the sacrificial material 1208.

FIGS. 15 and 16 show a top view and cross-sectional side view,respectively, of the probe material 1206 and sacrificial material 1208after they have been shaped by the electrode 1002 (as shown in FIGS.12-14). As shown, the electrode 1002 shapes the probe material 1206 anda first layer of sacrificial material 1501 (i.e., an upper layer oforiginal sacrificial material 1208) as defined by the cavities 1004 inthe electrode 1002. The probe material 1206 is then released from thesacrificial material 1208 and 1501, leaving loose probes 1510 made ofthe probe material 1206, as shown in FIG. 17. Alternatively, the EDMelectrode may be fashioned to leave small amounts of material (notshown) between the probes 1510, tying the probes together. This mayallow the probes to be further processed or handled in groups. It mayalso aid in handling the probes during later assembly. Preferably, suchtying material is left in sufficiently thin quantities that it is easilyremoved (e.g., broken) from the probes.

As mentioned above, the sacrificial material 1208 is not necessary. Theprobe material 1206 could be provided by itself, and the electrode 1002could simply etch through probe material 1206. Moreover, if used, thesacrificial material 1208 need not be shaped by the electrode 1002. Thatis, the electrode 1002 may be stopped in FIG. 14 just as it reaches thesacrificial material 1208 so that it etches only the probe material1206.

Regardless of whether or not the sacrificial material 1208 is etched,how the sacrificial material 1208 is adhered to and then released fromthe probe material 1206 is not critical to the invention. Likewise, thematerial used as the sacrificial material 1208 is not critical to theinvention. For example, the probe material 1206 and the sacrificialmaterial 1208 may be adhered together using any suitable adhesive (e.g.,epoxy, etc.). The probe material 1206 and the sacrificial material 1208may then be separated by dissolving, etching away, or otherwise removingthe adhesive. As another example, the sacrificial material 1208 may bedissolved or etched away to separate the probes 1510 from thesacrificial material.

As an alternative, the initial block of probe material 1206 may be acomposite material that includes one material for the bodies of probes1510 and a different material for the tips of probes 1510. For example,the initial block of material from which the result shown in FIG. 15 wasprocessed may include a rectangular swath of tip material across the topand across the bottom of the larger rectangular structure shown in FIG.15. (Exemplary swaths are shown in FIG. 15 in dashed lines and labeled1511.) Such swaths would be large enough to include the tips of probes1510 shown in FIG. 15. In this way, the probes 1510 may comprisemultiple materials (e.g., one material for the body of the probes, and a(different material for the tips of the probes). Alternatively, theentire block is made of the same material but the swaths 1511 arespecially treated, such as discussed above with respect to the probe ortip materials shown in FIG. 1.

An exemplary use of the loose probes 1510 shown in FIG. 17 isillustrated in FIGS. 18-21. Illustrated in FIGS. 18 and 19 is a basesubstrate 1812 with openings 1816 and solder 1814 around the openings1816. As shown in FIG. 20, probes 1510 may be inserted into the openings1816, and the solder 1814 flowed to secure the probes 1510 in theopenings 1816. As shown in FIG. 21, one or more such base substrates1812 may in turn be secured (e.g., by solder 1814, brazing, welding, orother means) to a larger substrate, such as an electronic component 2120with conductive terminals 2122. As an example, the electronic component2120 may be a space transformer for a probe card assembly, such as theprobe card assemblies disclosed in U.S. Pat. No. 5,974,662, issued Nov.2, 1999, which is incorporated herein by reference. The foregoingexemplary method of assembling loose probes into arrays of probes isdescribed in more detail in commonly assigned U.S. patent applicationSer. No. 10/202,712, filed Jul. 24, 2002, which is also incorporatedherein by reference.

Like the EDM electrode 201, the EDM electrode 1002 may be formed of anyconductive material. Also, the cavities 1004 may be patterned in theelectrode 1002 using any suitable method. For example, the cavities 1004may be etched, machined, etc. into the electrode 1002. As anotherexample, the cavities 1004 may be formed using laser ablation. As yetanother example, the sacrificial substrate 1208 (e.g., a silicon wafer)may be covered with a photo resist, and the photo resist patterned,developed, and removed, such that photo resist remains on thesacrificial substrate 1208 only where cavities 1004 are to be formed.The sacrificial substrate 1208 is then metalized (e.g., by plating,deposition, etc.), forming a bottom plate of the electrode around thepatterned photo resist, which is then removed, leaving cavities 1004 inthe newly formed bottom plate.

Advantages of the method of making the probe array according to thepresent invention include independent processing of two differentsubstrates. Therefore, the processing steps of the two stages can becarried out in parallel and independent of one another. Any errors ordefects that may be present require only a repetition of one set ofsteps. Also, the resultant probe array has through holes that providesupport along at least a segment of the probe. The support is especiallyadvantageous in a probe array with lateral contact movement or wiping(i.e., movement of the probes first laterally along the surface of thedevice under test, and then “bumping” over a terminal pad on the deviceunder test).

It will be understood by those skilled in the art that various changesin form and details may be made therein without departing from thespirit and scope of the invention as defined in the appended claims.Thus, the breadth and scope of the present invention should not belimited by any of the above-described exemplary embodiments, but shouldbe defined only in accordance with the following claims and theirequivalents.

1. A method of manufacturing comprising: removing with an electricdischarge machine (EDM) material from a block of material to form shapedcontact tips at first ends of probes, said shaped tips configured tocontact and thereby make electrical connections with terminals of anelectronic device wherein: said block of material comprises a layer oftip material and a layer of probe material; said removing comprisesremoving material from said tip material to form said shaped contacttips; and said tip material comprises at least one of palladium, gold,rhodium, nickel, cobalt, an alloy of palladium, an alloy of gold, analloy of rhodium, an alloy of nickel, and an alloy of cobalt.
 2. Amethod of manufacturing comprising: removing with an electric dischargemachine (EDM) material from a block of material to form shaped contacttips at first ends of probes, said shaped tips configured to contact andthereby make electrical connections with terminals of an electronicdevice; and cutting with an EDM said probes out of said block ofmaterial.
 3. The method of claim 2, wherein said cutting is in adirection from said first ends of said probes to second opposite ends ofsaid probes.
 4. The method of claim 2, wherein said cutting is in adirection from a first side profile of each of said probes to a secondopposite side profile of each of said probes.
 5. The method of claim 4,wherein said first side profiles include said first ends of said probesand second opposite ends of said probes.
 6. The method of claim 5,wherein each of said first side profiles comprises a base, a body withleast one change in direction, and one of said contact tips.
 7. Themethod of claim 2, wherein after said cutting, said probes are looseprobes.
 8. A method of manufacturing comprising: removing with anelectric discharge machine (EDM) material from a block of material toform shaped contact tips at first ends of probes, said shaped tipsconfigured to contact and thereby make electrical connections withterminals of an electronic device; and attaching ones of said probes toa substrate.
 9. The method of claim 8, further comprising formingelectrical connections on said substrate to said ones of said probes forconnecting to external signal sources.
 10. A method of manufacturing aplurality of probes, said method comprising: removing first materialfrom a block with an electric discharge machine comprising an electrodehaving a plurality of cavities therein, said cavities comprising shapesthat correspond to desired shapes of said probes, said removing leavingsecond material of said block corresponding to the cavities to form saidplurality of probes; and removing with and EDM a portion of said secondmaterial to form shaped contact tips at ends of said probes, whereinsaid second material comprises a plurality of layers of materials, andsaid removing a portion of said second material to form shaped contacttips at ends of said probes comprises removing a portion of one of saidlayers.
 11. A method of manufacturing a plurality of probes, said methodcomprising: removing first material from a block with an electricdischarge machine comprising an electrode having a plurality of cavitiestherein, said cavities comprising shapes that correspond to desiredshapes of said probes, said removing leaving second material of saidblock corresponding to the cavities to form said plurality of probes,wherein after said removing, said probes are loose probes.
 12. A methodof manufacturing a plurality of probes, said method comprising: removingfirst material from a block with an electric discharge machinecomprising an electrode having a plurality of cavities therein, saidcavities comprising shapes that correspond to desired shapes of saidprobes, said removing leaving second material of said blockcorresponding to the cavities to form said plurality of probes; andattaching ones of said probes to a substrate.
 13. The method of claim12, further comprising forming electrical connections on said substrateto said ones of said probes for connecting to external signal sources.